1) Pertaining to actual time during which a physical process transpires. 2) Pertaining to an application in which response to input is fast enough to effect subsequent input, as when conducting the dialog that takes place at terminals in interactive systems.
Fast enough, that is, multiple frames per second of display, with a tolerable lag time between an event and its display on the screen
The term to describe what can be processed fast enough to make it operate on the same time scale as real time does.